This invention relates to the coating of tubular members, such as stents.
During the manufacture of stents it is often necessary to coat a stent with a liquid. The liquid may be a biocompatible material or a coating which encases the stent with a material once the liquid has dried. Such coating has often been performed by manually dipping the stent in the liquid and then removing the stent and drying it. Such a process leads to manufacturing inconsistency. Furthermore, many stents have plural apertures formed in the surface thereof and the presence of excess liquid or inconsistent drying of the liquid can lead to such apertures becoming blocked unnecessarily.
The present invention seeks to overcome the above and other problems.
According to the present invention there is provided an apparatus for coating tubular members, such as stents, the apparatus comprising:
a liquid reservoir;
a stent support member for supporting, in use, a tubular member;
support member dipping means for placing the support member in the liquid reservoir in use and drawing the support member therefrom; and
pressure differential generating means for generating a pressure differential, wherein:
the stent support member is arranged to provide a central passageway through a stent placed thereon, the central passageway having a plurality of perforations formed therein, and
the pressure differential generating means is arranged to generate, in use, a pressure differential between the passageway and the tubular member.
The support member may be formed from a rigid hollow member, such as a needle, with apertures formed therein. The support member may alternatively be formed from a rigid member having a series of slots formed therein. With such an arrangement a sheath may be placed around the external periphery of the member to define a series of circular perforations. The support member may be formed from metal, a plastics material, or a combination thereof.
The pressure differential generating means may be a pump. The support member may have two collars and a central rigid support member, the collars arranged to engage with each end of a tubular member in use.
The dipping means may be arranged to enable inversion of the support member once it has been removed from the liquid reservoir.
The apparatus may further comprise a drying chamber into which a heated gas can be pumped to dry the tubular member on the support member after removal from the liquid reservoir.
Plural support members may be provided in the apparatus. Each support member may support plural stents.
A corresponding method is also provided.
The apparatus and method of the present invention provides a system which produces consistent coating results. Furthermore, because the pressure differential that is generated can prevent apertures becoming blocked with dried solution, stents with apertures that are produced by the apparatus and method are less likely to be rejected because of such blockages. In addition the apparatus and method can produce a thin coating (for example in the region 5 nm to 200 nm) on the inside of the stent whilst producing a thicker coating (for example 500 nm to 1500 nm) on the outside.